Development of a Design System for Permeable Interlocking Concrete Pavement

David Hein, P. Eng.Applied Research Associates, Inc., Toronto, Ontario, Canada David R. Smith, Technical DirectorInterlocking Concrete Pavement Institute, Herndon, Virginia USA

Permeable InterlockingConcrete PavementPICPPervious concrete Porous asphaltPermeable ICP 2

No. 8 (89 or 9)

No. 57

No. 2 (3 or 4)

Typical bedding, base & subbase ASTM / AASHTO stone sizes

Permeable PavementDesign

StructuralAnalysis

HydrologicalAnalysis

Traffic Load: ESALs,Traffic Index

Subgrade Characteristics:Mr, CBR, R-Value

Design Storm(s) Contributing AreaRunoff

Select the Limiting(Thicker) Cross-

Section for Design

Determine Surface & Base/Subbase

Thickness

Surface & Base/Subbase

Properties

StructurallyAdequate?

Determine Depth ofWater & Base/

Subbase thickness

Infiltration Rate &Volume Through

Subgrade

Outflow Rate &Volume Through

Underdrains

HydrologicallyAdequate?No Yes Yes No

Revise Thickness

Revise Thickness or

Adjust Outflow

Time StepsVehicular UsePedestrian Use

Based on 1993 AASHTO Guide – Flexible PavementsMinimum soil strength:4% soaked CBRR‐value = 9Resilient modulus = 6,200 psi (43 MPa) 

• Base/subbase Layer coefficients3 1/8 in. (80 mm) thick pavers + 2 in. (50 mm) bedding = 0.34 in. (100 mm) thick ASTM No. 57 stone base = 0.09Variable thickness ASTM No. 2, 3 or 4 stone subbase = 0.06(Typical dense‐graded base ~ 0.12 – 0.14)

No frost layer required

ICPI design chart: max. 1 million 18,000 lb (80 kN) ESALs or TI=9

PICP Structural Design

AASHTO Typical ESALs by Road Class

Road Class   Design ESALs        Arterial or Major StreetsUrban 7,500,000Rural 3,600,000Major CollectorsUrban 2,800,000Rural 1,450,000Minor CollectorsUrban 1,250,000Rural 550,000Commercial/Multi‐Family LocalsUrban  425,000Rural 275,000

Permeable Design Pro Software for PICP Design

Define PICP Pavement & Contributing Area

Select/Design Pavement Material Properties

Traffic Analysis for Structural Design

AASHTO Structural Design Analysis

Establish Hydrologic Conditions and Design Storms

Calculate Total Water In-Flow

Select Drainage Parameters and Conditions

Run

Ana

lysi

s

Select Base Thickness from Rainfall Event

Repeat Analysis to ‘Fine Tune’ PICP DesignInclude drain pipes as required

ICPI PICP Developments4th Edition PICP Manual100+ pages60+ figuresIndustry consensus• Hydrologic Design• Structural design

Up to 1 million lifetime ESALs or Caltrans TI = 9

Follows Permeable Design Prosoftware

• Guide specs• Construction guidelines

Promotes using contractors with ICPI PICP course certificate

• Maintenance guidelines

ConclusionsStructural Design• PICP, PA and PC use empirical structural design methods• PICP – accounts for truck traffic loads and soil strengths, provides 

base/subbase thicknesses• AASHTO ‘93 method reasonable for PICP• Open‐graded subbase/base – more research needed in saturated 

base & soil conditions • Testing needed using PA & PC bases for higher ESAL facilities• Expand use of permeable pavements 

Green infrastructure/retrofit

www.icpi.orgdsmith@icpi.org

Warrenville, IL